The present invention relates to electrically charged particle emission structures. It more particularly relates to a method of generating such particles and controlling their initial trajectory, to a field emission structure for practicing the method, and to a method of constructing the same.
Cathode structures using electrically charged polarized particle emission principles now are being relatively widely used and investigated as field emission cathodes. Miniaturized thin film field emission cathode arrays (called by many "Spindt" cathodes in view of the contributions of the inventor of the subject matter hereof) have attributes which make them more suitable than thermal and other cold cathode arrangements for many uses. For example, they provide high emission current density for minimum voltage operation, and most designs have a relatively small geometric size in the direction of electron production. Field emission cathode arrays typically include an electrically conductive base structure from which small needle-like electron emitting tips project. A control electrode structure is spaced from the base adjacent the emitting tips, and a control voltage differential is established between the base and the control electrode to cause the desired emission of electrons from the tips. An electrical insulator generally is sandwiched between the base and the control electrode to prevent breakdown of the voltage differential and provide mechanical support for the control electrode.
The electron emitting tips are typically grouped on the base at discrete locations to provide a plurality of spaced-apart emissions sites, although in some instances a single emitting tip is used for each site. Both the control electrode and the insulator have apertures at the emitting sites to enable emission of electrons at such locations. U.S. Pat. Nos. 3,665,241; 3,755,704; 3,789,471; 3,812,559; and 4,141,405 (all of which name the present applicant as a sole or joint inventor) and the paper entitled "Recent Progress in Low-Voltage Field Emission Cathode Development" Journal de Physique, Supplement to Vol. 45, No. 12 (December 1984), provide examples of field emission cathode arrays and methods of making or using the same.
While field emission cathodes have many desirable attributes, in the past relatively convoluted and complex designs have been provided in efforts to shape and direct beams of electrons, protons or ions produced by the same. U.S. Pat. Nos. 4,103,202; 4,178,531; 4,020,381; and 4,498,952 are examples of such designs having added structure for these purposes.